The present invention relates to an optical disk, an optical disk device, and an optical disk reproduction method, for recording/reproducing digital signals.
In recent years, optical disk devices have attracted attention as means for recording/reproducing a large capacity of data, and are under active technical developments for achieving higher recording density.
Presently prevailing rewritable optical disks include spiral-shaped groove tracks composed of concave and convex portions (each having a width of about 50%) formed on a surface of a disk substrate at a pitch of 1 to 1.6 xcexcm. On the surface of the substrate, a thin film including a recording material (e.g., Ge, Sb, and Te in the case of a phase-change type optical disk) as a component is formed by a method such as sputtering. The disk substrate is fabricated in the following manner. First, a stamper is produced from a prototype where concave grooves and pits for sector addresses and the like are formed by cutting by light beam irradiation. Using such a stamper, the disk substrates made of polycarbonate and the like are mass-produced. The rewritable optical disks require sector-unit management for data recording and reproduction. Accordingly, at the fabrication of the disks, concave and convex portions (pits) are often formed on a recording surface, simultaneously with the formation of guide grooves for tracking control, so as to record address information of each sector.
Each track of the optical disk with the above structure is irradiated with a light beam having a predetermined recording power, so as to form recording marks on the recording thin film. The portions irradiated with the light beam (the recording marks) have different optical characteristics (reflection characteristics) from the other portions of the recording thin film. Thus, the recorded information can be reproduced by irradiating the track with a predetermined reproduction power and detecting light reflected from the recording film.
In the following description, the pits of physical concave and convex portions and the recording marks obtained by a change in the optical characteristics of the recording thin film are generically referred to as xe2x80x9cmarksxe2x80x9d, unless otherwise specified. The pits are read-only marks once formed, while the recording marks are rewritable. At the reproduction of recorded information, the two types of marks are read as changes in the amplitude of reproduction signals. The concave and convex portions as used herein refers to the shapes as are viewed from a reproduction beginning of the optical disk device. In other words, the xe2x80x9cpitsxe2x80x9d refer to the convex portions as are viewed from the reproduction head, and the xe2x80x9cgroovesxe2x80x9d also refer to the convex portions.
Techniques for achieving an optical disk with a high recording density include increasing the recording density in the track direction and increasing the recording density in the linear velocity-direction.
Increasing the recording density in the track direction includes reducing the distance between tracks (the track pitch). One technique for reducing the track pitch is land/groove recording where signals are recorded both on convex tracks (groove portions) and concave tracks (land portions). The land/groove recording realizes double recording density, compared with the case of recording signals on either the groove portions or the land portions, if the other conditions are the same.
One technique for increasing the recording density in the linear velocity direction is referred to as mark length recording where both ends of a mark are made to correspond to xe2x80x9c1xe2x80x9d of modulation data. FIG. 1 illustrates an example of the mark length recording in comparison with inter-mark recording. Referring to FIG. 1, a sequence Y represents digital data modulated using a run length limit code. The run length limit code as used herein refers to a code sequence where the number of continuous xe2x80x9c0xe2x80x9ds interposed between every adjacent xe2x80x9c1xe2x80x9ds (hereinbelow, called the zero run) is limited to a predetermined number. The interval (length) from one xe2x80x9c1xe2x80x9d to the next xe2x80x9c1xe2x80x9d in the sequence Y is called an inversion interval. The limits, i.e., the minimum and maximum values of the inversion interval of the sequence Y are determined by the limitation of the zero run. Such values are called the minimum inversion interval and the maximum inversion interval.
When the sequence Y is recorded using the inter-mark recording (PPM; pit position modulation), the xe2x80x9c1xe2x80x9d of the sequence Y corresponds to a recording mark 101, and the zero run corresponds to a space 102. When the sequence Y is recorded using the mark length recording (PWM; pulse width modulation), the recording state, i.e., whether the recording mark 101 or the space 102, is switched by the appearance of xe2x80x9c1xe2x80x9d in the sequence Y. When the mark length recording is employed, the inversion interval corresponds to the length of the recording mark 101 or the space 102.
When a run length limit code of which the minimum inversion interval is 2 or more is used, the mark length recording may have an increased number of bits per unit length, compared with the inter-mark recording. For example, consider the case where the minimum value of the physical size of a mark which can be formed on a disk (called a mark unit) is the same in both the mark length recording and the inter-mark recording. As is observed from FIG. 1, while the inter-mark recording utilizes three mark units to record data of the minimum code length (three bits, xe2x80x9c100xe2x80x9d, in the sequence Y), the mark length recording utilizes only one mark unit. For example, while the recording density in the inter-mark recording is approximately 0.8 to 1.0 xcexcm/bit, the recording density in the mark length recording is approximately 0.4 xcexcm/bit.
In general, the tracks on the optical disk are divided into recording sectors which represent minimum access units. Address information is prerecorded on each recording sector as described above. By reading the address information, the access to the recording sectors for data recording/reproduction is possible.
FIG. 2A illustrates a signal format of each recording sector of a rewritable optical disk which is in accordance with ISO (see ISO/IEC 10090). A recording sector 103 begins with a header 104 where addressing information for reading address information is prerecorded by forming concave and convex portions on the recording surface. A recording field 105 stores user data where digital data is modulated using a (2,7) modulation code for the inter-mark recording. FIG. 3 shows a conversion table of (2,7) modulation codes. As is observed from FIG. 3, by the (2,7) modulation, i-bit digital data (i=2, 3, 4) is converted into a 2xc3x97i-bit code sequence. The (2,7) modulation codes are run length limit codes where the zero run is limited between 2 and 7.
FIG. 2B shows the construction of the header 104. A sector mark SM is provided so that the optical disk device can identify the beginning of the recording sector without clock reproduction by a phase locked loop (PLL). As shown in FIG. 2C, the sector mark SM includes a pattern using comparatively long marks. Since the sector mark SM has this predetermined pattern, and the amplitude of the reproduction signals thereof is large, the sector mark SM is distinguishable from other data recorded using the inter-mark recording. The position of the header 104 is detected by detecting the sector mark SM, thereby to reproduce the address information.
VFO regions VF01 and VF02 shown in FIG. 2B are provided so that the optical disk device can obtain bit synchronization of reproduction signals using a clock reproduction by the PLL. A 2-zero run sequential pattern is recorded using the inter-mark recording.
Address marks AM are provided so that the optical disk device can identify the byte synchronization of subsequent address fields ID1, ID2, and ID3. Each of the address marks AM includes a pattern as shown in FIG. 2D recorded using the inter-mark recording technique. The pattern of the address mark AM includes a pattern of Tmax+1=9 bits where Tmax is a maximum inversion interval of the (2,7) modulation code (Tmax=8). This pattern does not appear in data recorded by the (2,7) modulation code.
Each of the address fields ID1, ID2, and ID3 includes: address information composed of track numbers, sector numbers, and the like; and cyclic redundancy check (CRC) codes for error detection during data reproduction, which are subjected to the (2,7) modulation and recorded using the inter-mark recording.
A postamble PA is provided to indicate the end of the (2,7) modulated data in the address field ID3.
FIG. 4 shows an example of signal amplitudes obtained when information recorded on the header 104 is reproduced by the optical disk device. As is observed from FIG. 4, the amplitudes of the reproduced signals are proportional to the lengths of the corresponding marks. The amplitude of the reproduced signal of the sector mark SM which has a long length is larger than that of the reproduced signal of other data. This allows for the identification of the sector mark SM by detecting the envelope of the reproduced signal waveform, and thus the detection of the beginning of each recording sector.
In the above example, all of the (2,7) modulated data is recorded using the inter-mark recording. However, in an optical disk having the header 104, when data is recorded using the mark length recording for improving the recording density, the marks recorded in the address fields ID1 to ID3 of the header 104 and the marks recorded in the recording field 105 have a certain length determined by the zero run limitation of the modulation code. Accordingly, the amplitude of the reproduced signal of data recorded using the mark length recording becomes large, compared with that recorded using the inter-mark recording where each mark corresponds to the 1-bit long xe2x80x9c1xe2x80x9d. In the mark length recording, therefore, the difference in the signal amplitude (or the difference in the pattern) between the sector mark SM and the other portions becomes small compared with the case of the inter-mark recording. This makes it difficult to detect the beginning of the recording sector 103 by the envelope.
Moreover, when the above-described address mark AM is used, an erroneous detection of the address mark AM due to an erroneous bit shift of xe2x80x9c1xe2x80x9d may occur. For example, a code sequence obtained by the (2,7) modulation of digital data { . . . 10110011 . . . } is converted into { . . . 0100100000001000 . . . } from a conversion table such as that shown in FIG. 3. At this time, the pattern of the address mark AM is {0100100000000100} as shown in FIG. 2D. If xe2x80x9c1xe2x80x9d of the above (2,7) modulated pattern shifts by one bit, the resultant pattern is identical to the address pattern AM, which will cause erroneous detection.
In view of the foregoing, the objects of the present invention are to provide an optical disk, an optical disk device, and an optical disk reproduction method, where address information can be read reliably even when high recording density is achieved by employing mark length recording and the like.
The optical disk of the present invention includes a plurality of tracks each divided into a plurality of recording sectors, each of the recording sectors including a header region, wherein the header region includes address information for identifying a position of the corresponding recording sector and address synchronous information for identifying a recording position of the address information for bit synchronization. The address information has been modulated using a run length limit code of a maximum inversion interval of Tmax bits (Tmax is a natural number), and the address synchronous information includes two patterns of which inversion interval is (Tmax+3) bits or more, so that a reproduced signal of the address synchronous information is distinguished from a reproduced signal of other information. With the above construction, the above objects are attained.
In one embodiment, the address synchronous information includes a first pattern and a second pattern which are different in either a physical shape or an optical characteristic of a recording surface of the optical disk, and the address synchronous information includes one first pattern having a length of (Tmax+3) bits or more and one second pattern having a length of (Tmax+3) bits or more.
The pattern may be a convex portion (pit) formed physically on the recording surface of the optical disk, and the second pattern is a concave portion formed physically on the recording surface of the optical disk.
The first pattern may be a recording mark formed by changing a reflection characteristic of the recording surface of the optical disk, and the second pattern is a space on the recording surface.
Preferably, a total bit length of the first pattern included in the address synchronous information and a total bit length of the second pattern included in the address synchronous information are equal to each other.
Preferably, the header region includes four-time repetition of the address information and the address synchronous information.
The optical disk of this invention includes a plurality of tracks each divided into a plurality of recording sectors, each of the recording sectors including a header region, wherein the header region includes address information for identifying a position of the corresponding recording sector, address synchronous information for identifying a recording position of the address information for bit synchronization, and clock synchronous information for reproducing a clock signal, the address information has been modulated using a run length limit code of a minimum inversion interval of Tmin bits and a maximum inversion interval of Tmax bits (Tmax and Tmin are natural numbers satisfying Tmax greater than Tmin), the clock synchronous information is a sequential pattern of alternate repetition of d-bit long mark and space (d is a natural number satisfying Tminxe2x89xa6d less than Tmax), and the address synchronous information includes two patterns of which inversion interval is (Tmax+3) bits or more, so that a reproduced signal of the address synchronous information is distinguished from a reproduced signal of other information. With the above construction, the above objects are attained.
In one embodiment, each of the address synchronous information and the clock synchronous information includes a first pattern and a second pattern which are different in either a physical shape or an optical characteristic of a recording surface of the optical disk, and the address synchronous information includes one first pattern having a length of (Tmax+3) bits or more and one second pattern having a length of (Tmax+3) bits or more.
In another embodiment, the minimum inversion interval Tmin is 3, the maximum inversion interval Tmax is 11, and the value d is 3.
In still another embodiment, the minimum inversion interval Tmin is 3, the maximum inversion interval Tmax is 11, and the value d is 4.
Preferably, the header region includes four-time repetition of the clock synchronous information, the address information, and the address synchronous information.
The optical disk comprising a plurality of tracks each divided into a plurality of recording sectors, wherein each recording sector includes a header region and a postamble region following an end of the header region, and the postamble region includes a pattern determined based on a modulation result of data of the header region. With above construction, the above objects are attained.
In one embodiment, the data on the header region is modulated using a modulation code for performing a conversion in a table based on a state, the postamble region includes information for identifying the state.
The information for identifying the state may be at least one specific bit having a predetermined value, and a bit located adjacent to the specific bit has substantially the same value as the predetermined value of the specific bit.
The optical disk of this invention includes a plurality of tracks each divided into a plurality of recording sectors, wherein each recording sector includes a header region, a data recording region, and a postamble region following an end of the data recording region, and the postamble region includes a pattern determined based on a modulation result of data of the data recording region. With this construction, the above objects are attained.
In one embodiment, the data on the data recording region is modulated using a modulation code for performing conversion in a table based on a state, the postamble region includes information for identifying the state.
The information for identifying the state may be at least one specific bit having a predetermined value, and a bit located adjacent to the specific bit has substantially the same value as the predetermined value of the specific bit.
In one embodiment, the recording sector further includes a guard data recording region following the postamble region for recording dummy data.
In another embodiment, the data recording region includes data modulated using a run length limit code of a minimum inversion interval of Tmin bits and a maximum inversion interval of Tmax bits (Tmax and Tmin are natural numbers satisfying Tmax greater than Tmin), and the guard data recording region includes a pattern of alternate repetition of a k-bit long optical mark and a k-bit long optical space (k is a natural number satisfying Tminxe2x89xa6kxe2x89xa6Tmax)
The optical disk of this invention includes a plurality of tracks each divided into a plurality of recording sectors, wherein each recording sector includes a header region, and the header region includes an address region having a postamble region at an end of the address region, and the postamble region has a pattern which ends with non-pit data or a space. With this construction, the above objects are attained.
The header region may include a plurality of the address regions.
The address regions may be located in the middle of groove portions and land portions of the tracks.
The optical disk of this invention includes a plurality of tracks each divided into a plurality of recording sectors, wherein each recording sector includes a header region, the header region includes a plurality of address regions, each of the address regions includes a VFO region at a beginning of the address region, and the VFO region has a pattern which starts with non-pit data or a space. With this construction, the above objects are attained.
In one embodiment, the address region includes an address information region where address information is recorded by a mark length recording for identifying a position of the corresponding recording sector, and the address information is modulated using a run length limit code of a minimum inversion interval of Tmin bits and a maximum inversion interval of Tmax bits (Tmax and Tmin are natural numbers satisfying Tmax greater than Tmin), and non-pit data or a space having a length in a range of Tmin bits or more and Tmax bits or less is provided between the address regions.
The address regions may be located in the middle of groove portions and land portions of the tracks.
The optical disk device of this invention is for an optical disk including a plurality of tracks each divided into a plurality of recording sectors, each recording sector including a header region and a data region, the header region including address information for identifying a position of the corresponding recording sector, address synchronous information for identifying a recording position of the address information for bit synchronization, and clock synchronous information having a predetermined sequential pattern, the device comprising: means for reading a reproduced signal from the optical disk; address reproduction means for obtaining the address information from the reproduced signal; detection means for detecting the sequential pattern of the clock synchronous information from the reproduced signal to output a detection signal; and address reproduction permit means for permitting the address reproduction means to perform a read operation of the address information based on the detection signal. With this construction, the above objects are attained.
In one embodiment, the optical disk device further includes: clock generation means for generating a clock signal from the reproduced signal; and clock reproduction permit signal for permitting the clock generation means to perform an operation of generating the clock signal based on the detection signal.
The detection means may includes: binary means for converting the reproduced signal into binary data to output the binary data; sampling-means for sampling the binary data at a predetermined frequency to output digital data; parallel conversion means for converting the digital data into parallel data of at least mxc3x97n bits (m and n are natural numbers); and a detection table for detecting a predetermined sequence composed of n-time repetition of an m-bit pattern from the parallel data.
The optical disk device of this invention is for an optical disk including a plurality of tracks each divided into a plurality of recording sectors, each recording sector including a header region and a data region, the header region including address information for identifying a position of the corresponding recording sector, address synchronous information for identifying a recording position of the address information for bit synchronization, and clock synchronous information having a predetermined sequential pattern, the device comprising: means for reading a reproduced signal from the optical disk; clock generation means for generating a clock signal from the reproduced signal; detection means for detecting the sequential pattern of the clock synchronous information from the reproduced signal to output a detection signal; and clock reproduction permit means for permitting the clock generation means to perform an operation of generating the clock signal based on the detection signal.
In one embodiment, the detection means comprises: binary means for converting the reproduced signal into binary data to output the binary data; sampling means for sampling the binary data at a predetermined frequency to output digital data; parallel conversion means for converting the digital data into parallel data of at least mxc3x97n bits (m and n are natural numbers); and a detection table for detecting a predetermined sequence composed of n-time repetition of an m-bit pattern from the parallel data.
The reproduction method of this invention is for an optical disk including a plurality of tracks each divided into a plurality of recording sectors, each recording sector including a header region and a data region, the header region including address information for identifying a position of the corresponding recording sector, address synchronous information for identifying a recording position of the address information for bit synchronization, and clock synchronous information having a predetermined sequential pattern, the method comprising the steps of: retrieving a reproduced signal from the optical disk; detecting the sequential pattern of the clock synchronous information from the reproduced signal; permitting reading of the address information if the sequential pattern is detected; reading the address information from the reproduced signal in response to the permission; and terminating the step of reading the address information in a predetermined time period after the permission to return to the step of detecting the sequential pattern. With this construction, the above objects are attained.
In one embodiment, the reproduction method further includes the steps of: permitting reproduction of a clock signal if the sequential pattern is detected; and reproducing the clock signal from the reproduced signal in response to the permission.
The reproduction method of this invention is for an optical disk including a plurality of tracks each divided into a plurality of recording sectors, each recording sector including a header region and a data region, the header region including address information for identifying a position of the corresponding recording sector, address synchronous information for identifying a recording position of the address information for bit synchronization, and clock synchronous information having a predetermined sequential pattern, the method comprising the steps of: retrieving a reproduced signal from the optical disk; detecting the sequential pattern of the clock synchronous information from the reproduced signal; permitting reproduction of a clock signal if the sequential pattern is detected; and reproducing the clock signal from the reproduced signal in response to the permission. With this construction, the above objects are attained.
The reproduction method of this invention is for an optical disk including a plurality of tracks each divided into a plurality of recording sectors, each recording sector including a header region and a data region, the header region including address information for identifying a position of the corresponding recording sector, address synchronous information for identifying a recording position of the address information for bit synchronization, and clock synchronous information having a predetermined sequential pattern, the method comprising the steps of: retrieving a reproduced signal from the optical disk; determining a reproduction mode whether the reproduction mode is an initial mode during a time period from switching-on of the device or a track jump until the address information is first read from the reproduced signal or a normal mode during a time period from the reading of the address information until a next track jump is generated; detecting the sequential pattern of the clock synchronous information from the reproduced signal; permitting reading of the address information if the sequential pattern is detected in the initial mode as a first permitting step; reading the address information from the reproduced signal in response to the permission; generating a sector pulse if the address information is correctly read; permitting reading of the address information from the reproduced signal based on the sector pulse in the normal mode as a second permitting step; and terminating the reading of the address information to return to the step of determining a reproduction mode if the address information fails to be read within a predetermined time period after either the first or second permission step. With this construction, the above objects are attained.